The power of eggshells
By David Manly
Jan. 23, 2013 – Eggs are an important source of protein and a staple breakfast food, but with every egg eaten, a potentially useful source of energy storage is thrown away in the garbage – the shells.
David Miltlin’s research group at the University of Alberta and the National Research Council’s National Institute of nanotechnology have devised a way to create high performance electrochemical energy storage (known as supercapacitors) using low cost biowaste, such as eggshells.
According to Zhi Li, the postdoctoral researcher leading the project, the idea stemmed from reading about the structure and chemistry of eggshell membranes. Upon further investigation, the eggshell membranes obtained from the biowaste were found to be more efficient than the activated charcoal used in traditional supercapacitors.
“The eggshell membrane has a 3D network structure which allows fast electron transfer and therefore the carbonized eggshell membrane can work at much higher current than traditional activated carbons,” he explained. In addition, the membranes have much more nitrogen functionalities compared to normal carbon materials, which allows the to store a much larger charge.
The process of creating the carbonized eggshell membrane is simple and scalable says Li: the first step is to carbonize the eggshell through a pyrolysis process at a temperature of 800 C. Then, it is activated in air at 300 C to generate micropores on the surface, which increase the surface area available to hold an electric charge.
A procedure is currently in development to produce the eggshell material at a more industrial scale. Beyond that, the next step is to commercialize the technology, as well as to find further application for the new material.
“We have demonstrated its application as electrode materials for a supercapacitor,” said Li. “However, it is also a very interesting material for Lithium-ion batteries and electrochemical catalysis.”